Membrane filtration, consisting of ultrafiltration (UF) and microfiltration (MF), has experienced explosive growth as an alternative filtration technology for potable water production. The widespread interest in this technology is primarily because membrane filtration can be more effective at removing microorganisms than conventional granular filtration, and the ability toremove microorganisms is a key issue in drinking water production. Despite this growth, fundamental questions about the performance of membrane systems remain unanswered. An important concern has to do with the ability of dissolved organic matter (DOM) to foul membranes, and the subsequent loss of membrane performance resulting from this process. A series of experiments were conducted to investigate the fundamental interactions between dissolved organic matter in the source water and membrane surfaces. Specifically, the following questions are being addressed in this research: is the DOM that fouls membranes colloidal or molecular; if colloidal, are the colloids physically sieved from the water or adsorbed to the membrane; are particular fractions of DOM primarily responsible for fouling, or conversely, are there fractions of DOM which do not foul membranes at all; and, what is the functional group chemistry of the fouling species? This research is ongoing; this manuscript presents only preliminary results, which need to be substantiated with additional experimentation and analysis. Includes 8 references, table, figures.